1. Field of the Invention
The present invention relates to improved diarylide dyestuffs which exhibit improved solubility in organic solvents and which are particularly useful as light absorbers in photosensitive compositions.
2. Description of Related Art
Diazo pigments and dyestuffs are known in the art and have long been used in the preparation of printing inks and dyeing formulations. The so-called benzidine orange or yellow pigments are prepared by coupling a tetraazotized 3,3'-dichlorobenzidine with a pyrazolone-(5) coupling agent such as 1-phenyl-3-methyl-5-pyrazolone.
Most materials of this category are classified as pigments because they are generally insoluble in water as well as most organic solvents. These pigments must be ground to fine powders to form suspensions prior to use in coloring applications. This poor solubility limits the use of such materials in applications where solvent solubility is required, particularly their use as absorptive dyestuffs in solvent based photosensitive formulations such as photoresists.
Thus, the highly desirable absorption properties of these materials in the Deep UV (200-300 nm) or Near UV (300-450nm) regions of the spectrum which would make them excellent candidates as anti-halation agents or sensitizers in photosensitive applications are not advantageously used in some applications because of poor or non-existent solubility in the common organic solvents used in photosensitive formulations. Example of pigments of this type are disclosed in U.S. Pat. No. 3,776,749. Analogous pigments based on tetraazotized 4,4'-diamino-benzanilide coupled with 1-phenyl-3-methyl-5-pyrazolone are disclosed in U.S. Pat. No. 4,296,028.
Solvent soluble dyestuffs have been prepared by coupling a tetraazotized 4,4'-(hexafluoroisopropylidene) dianiline with either phenol or N-2-cyanoethyl N-ethyl m-toluidine, as disclosed in U.S. Pat. No. 3,310,573. However these dyestuffs are not disclosed to have spectral or other properties which would render them desirable as solvent soluble counterparts of the benzidine pigments referred to above.